Circumventing brittleness of 3D-printed Al₂O₃ cellular ceramic structures via compositing with polyurea

Benefiting from excellent mechanical properties and low density, cellular ceramic structures (CCSs) are competitive candidates as structural components. However, inherent brittleness from strong chemical bonds among atoms extremely impeded CCSs’ application. Natural materials occupied outstanding strength and toughness simultaneously due to the dual-phase interpenetrated structure. Inspired by natural materials, it was proposed to fabricate coating covered and fulfilled polyurea/CCS interpenetrated composites (C/CCSs and B/CCSs) to circumvent the brittleness of 3D-printed Al₂O₃ CCSs. It was demonstrated that polyurea coating had less effect on the compressive strength of C/CCSs but tremendously improved their energy-absorbing ability. The energy-absorbing ability of C/CCSs was improved from 26.48–52.57 kJ·m⁻³ of CCSs to 1.04–1.89 MJ·m⁻³ because of the extended plateau stage. Furthermore, compressive strength and energy-absorbing ability of B/CCSs were strengthened to 1.33–1.36 and 2.84–4.61 times of C/CCSs, respectively. Besides, failure mode of C/CCSs changed from localized deformation to fracturing entirely with the increase in relative density of CCSs inside, which was the same as that of CCSs. However, with the help of polyurea coating, C/CCSs were still intact at strains up to 60%, which would never fail catastrophically as CCSs at low strains. B/CCSs tended to fracture as a whole, which was not influenced by relative density of pristine CCSs. It was believed that this work provided a creative way to circumvent the brittleness of CCSs and improve their mechanical performances. Graphical abstract: (Figure presented.)